Process for preparing delta 9, 11 and 21-chlorocorticosteroids

ABSTRACT

Described is a process for the regioselective dehydration of 11-hydroxy steroids using PCl 5 , PCl 3 , POCl 3  or either SO 2  Cl 2  and imidazole, or PPh 3  and CCl 4 . The disclosed process selectively forms Δ 9 ,11 steroids from either 11-α- or 11-β-hydroxy steroids, and can also be used for the one-step conversion of 11,21 -dihydroxy steroids to 21-chloro-Δ 9 ,11 steroids. Also disclosed are processes for the regioselective conversion of 11-β-chloro steroids to Δ 9 ,11 steroids, and for regioselectively converting an 11,17,21-trihydroxy streoid to a 21-chloro-11,17-dihydroxy steroid.

The present application is the United States national application corresponding to International Application No. PCT/US95/06600, filed May 30, 1995 and designating the United States, which PCT application is in turn a continuation of U.S. application Ser. No. 08/252,302, filed Jun. 1, 1994 now U.S. Pat. No. 5,502,222.

BACKGROUND OF THE INVENTION

The synthesis of corticosteroids having therapeutic utility, such as mometasone, betamethasone and beclomethasone, requires functionalization of the C-9 and C-11 positions of the steroid molecule. The functionality is generally introduced via Δ⁹,11 steroid intermediates.

Methods for preparing steroids having a 9,11 double bond are known in the art. For example, an 11-hydroxy steroid can be converted to the corresponding mesylate (by treating with mesyl chloride) which is transformed into a Δ⁹,11 steroid via an elimination reaction. However, the prior art methods are not regiospecific in the case of 11α-hydroxy steroids and typically lead to mixtures of Δ⁹,11 steroid containing 10-15% of the analogous Δ⁹,12 steroids. Separation of these regio-isomeric products is difficult, generally requiring laborious physical separation procedures, resulting in increased costs and lower yields. It would therefore be desirable to develop an efficient regioselective method for preparing Δ⁹,11 steroids, from either 11α- or 11β-hydroxy steroids, for use as intermediates in the synthesis of corticosteroids.

The introduction of a 21-chloro group is also of commercial importance, e.g. for preparing intermediates and therapeutically important compounds such as mometasone. The conversion of 21-hydroxy steroids to the analogous 21-chloro steroid by chloride displacement of a 21-methanesulfonyl intermediate is known. However, this reaction is not regioselective in the case of 11-hydroxy steroids, as methanesulfonyl chloride reacts with both the 11- and 21-hydroxy groups. In addition, Wuts, et al., Syn. Comm., 23, (15) 2199-2211 (1993) describes a method for preparing 21-chloro steroids using the Vilsmeier reagent (prepared from DMF and POCl₃ or phosgene).

DE 1,127,895 describes the preparation of 9(11)-unsaturated steroids from the corresponding 11α-sulfonate esters by reaction with a lithium halide in an anhydrous basic solvent.

J. Org. Chem., Vol. 31 (1), pages 26-31 (1966) describes the conversion of 16β-methyl-11α,17,21-trihydroxy-1,4-pregnadiene-3,20-dione 21-acetate 11-mesylate into the corresponding 1,4,9(11 )-triene by reaction with sodium acetate in acetic acid.

J.A.C.S. Vol. 80(16), page 4431 (1958) describes the conversion of 11α,17α,21-trihydroxy-16α-methyl-1,4-pregnadiene-3,20-dione 21-acetate 11 -tosylate into the corresponding 1,4,9(11)-triene by reaction with sodium acetate in acetic acid.

Reissue Pat. No. 28,369 describes (in Example 20) the 9,11 -dehydration of 11β,17α,21-trihydroxy-16β-methyl-4-pregnene-3,20-dione 21-acetate with methanesulfonyl chloride in pyridine and DMF to the corresponding 4,9(11 )-pregnadiene.

EPA 3,341 describes (in Example 50) the conversion of 9α-fluoro-11β,21-dihydroxy-17α-methoxymethoxy-1,4-pregnadiene-3,20-dione 21-tosylate into 21-chloro-9α-fluoro-11β-hydroxy-17α-methoxymethoxy-1,4-pregnadiene-3,20-dione by reaction with lithium chloride in hexamethylphosphoramide.

U.S. Pat. No. 3,639,434 shows (in the scheme in the middle of column 5) the conversion of 11α,17α,21-trihydroxy-1,4-pregnadiene-3,20-dione 21-mesylate into 21-chloro-11α,17α,21-trihydroxy-1,4-pregnadiene-3,20-dione with lithium chloride in DMF.

In view of the importance of both 21-chloro groups and 9,11 -double bonds it would be desirable to develop a one-step process for efficiently introducing both functional groups in a single steroid molecule

SUMMARY OF THE INVENTION

The present invention provides a regioselective process for preparing Δ⁹,11 steroids of the formula I ##STR1## wherein: one of R² or R³ is CH₃ and the other is H; and X is H, halogeno or --OR, wherein R is H or --C(O)R¹, and R¹ is CF₃, C₁ -C₆ alkyl or C₁ -C₆ alkoxy.

The process of the present invention is chemically efficient, and where a Δ⁹,11 group and a 21-chloro group are required, allows the one step introduction of both functional groups.

The instantly claimed process comprises treating an 11-α-hydroxy steroid of the formula II or an 11-β-hydroxy steroid of the formula IV ##STR2## wherein Q is --OSO₂ C₆ H₄ CH₃, --OSO₂ CH₃, --O--C(O)O--B or X, wherein B is a group of the formula ##STR3## and wherein X, R² and R³ are as defined above, with PCl₅, PCl₃, POCl₃ or either SO₂ Cl₂ and imidazole, or PPh₃ and CCl₄, to form a compound of the formula I.

The present invention also provides a process for regioselectively preparing a 21-chloro steroid of the formula ##STR4## wherein one of R² or R³ is CH₃ and the other is H, comprising treating a triol of the formula ##STR5## wherein R² and R³ are as defined above, with either triphenylphosphine and CCl₄ or p-toluenesifonyl chloride and LiCl.

In an alternative embodiment the present invention further provides a process for preparing Δ⁹,11 steroids of the formula I, wherein X, R² and R³ are as defined above, comprising heating an 11-β-chloro steroid of the formula III ##STR6## wherein X, R² and R³ are as defined above, in the presence of a polar solvent to form a compound of the formula I. Preferably the polar solvent is DMSO, DMF or a mixture of CH₃ CN and water, diglyme and water, or dioxane and water.

DETAILED DESCRIPTION

As used herein, the term "alkyl" means, a straight or branched unsaturated hydrocarbon chain having from 1 to 6 carbon atoms and "alkoxy" similarly refers to an alkoxy group having from 1 to 6 carbon atoms;

"halogeno" means bromo, chloro or iodo;

"Tertiary amine base" means pyridine or a trialkylamine such as triethylamine, N-ethylpiperidine, DMAP or Hunigs base, or combinations thereof.

The following solvents and reagents employed in the process of the present invention are identified by the abbreviations indicated: ethyl acetate (EtOAc); acetic acid (HOAc); tetrahydrofuran (THF); dimethylsulfoxide (DMSO); triethylamine (Et₃ N); diisopropylethylamine (Hunigs base); methanol (MeOH); 1,8-diazabicyclo 5.4.0!undec-7-ene (DBU); triphenylphosphine (PPh₃); diisopropyl ether (iPr₂ O); dimethoxyethane (DME); t-butylmethyl ether (t--BuOMe); N,N-dimethylaminopyridine (DMAP); dimethylformamide (DMF); p-toluenesulfonyl chloride (TsCl).

The present invention comprises a process, designated Process A, for regio-selectively dehydrating an 11-hydroxy steroid of the formula II or IV to form a Δ⁹,11 steroid of the formula I, as shown in Reaction Scheme A. ##STR7##

In Step A1(a) an 1-hydroxy steroid II(a), e.g. a compound of formula II wherein X is --OR and R is H, is treated with an alkylchloroformate of the formula ClCO₂ R⁴, where R⁴ is C₁ -C₆ alkyl, preferably ethylchloroformate, and a tertiary amine base, preferably N-ethylpiperidine, Hunigs base or Et₃ N, to form a compound of formula II(b), e.g. a compound of the formula II wherein Q is or X or --O--C(O)O--B, wherein B is as defined above, X is --OR, R is --C(O)R¹ and R¹ is C₁ -C₆ alkoxy.

Alternatively, in Step A1(b) compound II(a) is treated with (CF₃ CO)₂ O or an acylating agent of the formula R⁴ C(O)L, wherein R⁴ is as defined above and L is a suitable leaving group such as halogeno, and a tertiary amine base, such as pyridine, optionally in the presence of DMAP, to form a compound of the formula II(c), e.g. a compound of the formula II wherein Q is X, X is --OR, R is --C(O)R¹ and R¹ is CF₃ or C₁ -C₆ alkyl.

In a second alternative, shown above as Step A1(c), compound II(a) is treated with a sulfonyl chloride of the formula ClSO₂ R⁵, wherein R⁵ is --C₆ H₄ CH₃, in the presence of a tertiary amine base, preferably Et₃ N, DMAP or a mixture of Et₃ N and DMAP, at -20° to 60° C., preferably at 0° to 40° C., and most preferably at 10° to 30° C., to form a compound of the formula II(d), e.g. a compound of the formula II wherein Q is X, X is --OSO₂ R⁵ and R⁵ is --C₆ H₄ CH₃.

In Step A2, a compound of the formula II(e), e.g. a compound of the formula II wherein Q is X and X is H or halogeno, or a compound of the formula II(a), II(b), II(c) or II(d), is treated with PCl₅, PCl₃, POCl₃ or either SO₂ Cl₂ and imidazole, or PPh₃ and CCl₄. Where the reaction is carried out using PCl₅, it is preferably run at low temperature, e.g. at 0° to -100° C., preferably at -40° to -90° C., and most preferably at about -60° C. to -85° C., in a suitable organic solvent such as THF, to form a Δ⁹,11 steroid of the formula I.

Where Step A2 is carried out using PPh₃ and CCl₄., the reaction is run at 0° to 100° C., preferably at 20° to 80° C., in a suitable solvent, such as CH₃ CN. Where SO₂ Cl₂ and imidazole are used in Step A2, the reaction is carried out in a suitable solvent, such as THF, at 0° to -100° C., preferably about -10° to -80° C., and most preferably at -20° to -78° C. Finally, where POCl₃ is used, Step A2 is carried out in the presence of pyridine in a suitable solvent, such as CH₂ Cl₂, at -40° to 100° C., preferably at -20° to 80° C., and most preferably at -5° to 60° C. When PCl₃ is used in Step A2, the reaction is preferably carried out at -80° to 50° C., preferably at -40° to 30° C., and most preferably at -20° to 25° C.

Compounds of the formula I wherein X is --OR and R is --C(O)R¹ can be converted to compounds of the formula I wherein X is --OR, and R is H, by hydrolysis using known methods. In addition, compounds of the formula I wherein X is --OR, and R is H, can be converted to compounds of the formula I wherein X is halogeno, via known methods.

The present invention further comprises Process A as shown above wherein the analogous 11-p-hydroxy steroid, e.g. a compound of the formula IV, is used in place of the 11-α-hydroxy steroid (II).

Starting compounds of the formula II(a) and II(e), and the analogous compounds of the formula IV are known and can be prepared by established methods.

The Δ⁹,11 steroids prepared by the Process A of the present invention are of high purity and preferably contain less than 2% of the unwanted Δ¹¹,12 regio-isomers.

The present invention also comprises a process for regioselectively converting an 11,17,21-trihydroxy steroid to a 21-chloro-11,17-dihydroxy steroid as shown in Reaction Scheme AA. ##STR8##

In Reaction Scheme AA, a compound of the formula II(a) is treated with PPh₃ and CCl₄ in the presence of a suitable solvent, such as CH₃ CN, at -20° to 40° C., preferably at 0° to 30° C., and most preferably at 20° to 30° C., to selectively form a compound of the formula II(f), i.e., a compound of the formula II wherein Q is X and X is Cl.

Alternatively, in Reaction Scheme AA, a compound of the formula II(a) is treated with TsCl and a tertiary amine base, such as Et₃ N or a combination of Et₃ N and DMAP, in a suitable sovent, such as CH₂ Cl₂, at -20° to 40° C., preferably at 0° to 30° C., and most preferably at about room temperature, to form a 21-tosylate intermediate, which is then treated with LiCl at 20° to 60° , preferably at 30° to 50° and most preferably at about 40° C., to form the 21-chloride II(f).

The present invention further provides a Process AA as shown above wherein the analogous 11-β-hydroxy steroid, e.g. a compound of the formula IV, is used in place of the 11-α-hydroxy steroid II(a).

In an alternative embodiment, the present invention comprises a process, designated Process B, for regio-selectively converting an 11-β-chloro steroid of the formula III to form a Δ⁹,11 steroid of the formula I, as shown in Reaction Scheme B. ##STR9##

In Reaction Scheme B a compound of the formula III is combined with a suitable polar solvent, preferably DMSO, DMF or a mixture of CH₃ CN and water, diglyme and water, or dioxane and water. The reaction is generally carried out at 20° to 150° C. Typically for compounds III wherein X is --OR and R is H, the reaction is preferably carried out at 20° to 80° , and most preferably at 30° to 50° C., while for compounds III where X is H, halogeno or --OR wherein R is --C(O)R¹, the reaction is preferably carried out at 50° to 150° C., more preferably at 80° to 120° C., and most preferably at 90° to 110° C., to form a compound of formula I.

Chloro substituted steroids of the formula III can be prepared by established methods. For example, treating a steroid of the formula II with a chlorinating agent, such as PCl₃, PCl₅ /pyridine, or CCl₄ /PPh₃, provides the 11-β-chloro steroid III as one of the products. Compounds of the formula II are known and can be prepared via methods disclosed in the prior art.

The following preparations and examples are illustrative of the process of the present invention.

GENERAL METHODS

The ratios of Δ⁹,11 to Δ¹¹,12 steroids, and the percentages of Δ⁹,11, Δ¹¹,12 and 11-β-chloro steroids, presented in the Examples below were determined via HPLC analysis (μ-Bondapak® C-18 column, 1:1 CH₃ CN/H₂ O, 1-2 mL/min., U.V. detector at 254 nm) of the products.

Molar yields are based on the quantity of starting compound and product, corrected for starting compound and product purity, as determined by HPLC using the above conditions. ##STR10##

Combine 20.0 g of 16β-methyl-11α,17α, 21-trihydroxy-pregna-1,4-diene-3,20-dione, 80 mL of CH₂ Cl₂ and 30 mL of Et₃ N. Stir the mixture, cool to -15° to -10° C. and slowly add a solution of 6.5 mL of ClCO₂ CH₂ CH₃ in 10 mL. of CH₂ Cl₂ over a period of 1 h, while maintaining the temperature at -15° to -10° C. Stir the mixture at -15° to -10° C. for 30 min, then warm to 20° to 25° C. and stir for 2 to 4 h more. Add 40 mL of THF and 80 mL of water, then stir at 20° to 25° C. while slowly adding 13 mL of concentrated HCl to adjust the pH to 2. Stir for 15 min more then recheck the pH. (If the pH is >2 then add HCl to adjust to pH 2 and stir 30 min more.) Allow the mixture to settle and separate the layers. Extract the aqueous layer with 50 mL of CH₂ Cl₂, combine the extract with the original organic layer and heat the combined organic solution to distill to a volume of 40 mL. Cool the concentrated solution, add 40 mL of THF, then heat again to distill to a volume of 40 mL. Cool to give a solution of the title compound for use in Example 1.

Alternatively, the title compound can be isolated from the product solution, e.g. by concentration in vacuo, and if necessary purified. ##STR11##

The title compound is prepared by treating a mixture of 0.050 g of 16β-methyl-11β,17α,21 -trihydroxypregna-1,4-diene-3,20-dione, 2 mL of CH₂ Cl₂ and 0.1 mL of Et₃ N, with 0.5 mL of a solution of 0.3 mL of ClCO₂ CH₂ CH₃ in 10 mL of CH₂ Cl₂ via essentially the same procedure as described for Preparation 1. ##STR12##

The title compound is prepared by treating a mixture of 2 g of 16α-methyl-11α,17α,21-trihydroxypregna-1,4-diene-3,20-dione, 15 mL of CH₂ Cl₂ and 3 mL of Et₃ N, with a solution of 0.65 mL of ClCO₂ CH₂ CH₃ in 2 mL of CH₂ Cl₂ via essentially the same procedure as described for Preparation 1. ##STR13##

Combine 2 g of the isolated product of Preparation 1 with 30 mL of CH₂ Cl₂ and 6 mL of pyridine. Add an excess of PCl₅ and stir the mixture at room temperature for 30 min. Quench the reaction mixture by adding water, then dilute with 100 mL of CH₂ Cl₂. Wash the resulting solution with 50 mL of 6N HCl (aqueous), separate the organic and aqueous layers, and extract the aqueous layer with CH₂ Cl₂ (2×50 mL). Combine the organic solutions, wash successively with 1 N HCl (aqueous), water and brine, then dry over Na₂ SO₄. Concentrate the organic solution in vacuo to a residue, then purify the residue by chromatography (silica gel, 30/70 then 50/50 EtOAc/hexane) to give 0.15 g of the title compound. ¹ H NMR (CDCl₃): 7.20 (d, J=10 Hz); 6.28 (d, J=10 Hz); 5.97 (s); 4.98 (d, J=18 Hz); 4.85 (d, J=18 Hz); 4.62 (br. s); 4.21 (q, J=7 Hz); 2.6-2.0 (m); 1.5 (s); 1.31 (t, J=7 Hz); 1.15 (d, J=7 Hz); 1.1 (s). Mass Spectrum (FAB): (M⁺ +3) 467; (M⁺ +1) 465; (M⁺ +1-HCl) 429.

Alternatively, the 11-β-chloro steroid is prepared by treating a solution of the product of Preparation 1 in THF with 2 equiv. of PCl₃ under substantially the same conditions as described above for 4.5 h. The title compound is then isolated as described above. ##STR14##

Combine 1 g of the isolated product of Preparation 1 with 10 mL of THF and 5 mL of CCl₄. Add 1 g of PPh₃ and stir the mixture at 70° C. for 1 h. The product is isolated via substantially the same procedure as described for Preparation 2 to give the title compound. ##STR15##

Cool 2 g of 16α-methyl-11α,17α, 21-trihydroxy-pregna-1,4-diene-3,20-dione to -20° C. Add 15 mL of THF then slowly add (at a rate of 0.2 mL/min) a solution of 0.8 mL of (CF₃ CO)₂ O in 5 mL of THF and stir the mixture at -20° C. Add another 0.05 mL of (CF₃ CO)₂ O in 1 mL of THF and stir at -20° C. to give a solution of the trifluoroacetyl ester product. ##STR16##

Combine 2 g of 16α-methyl-11α,17α, 21-trihydroxy-pregna-1,4-diene-3,20-dione, 34 mg (0.05 equivalents) of DMAP, 14 mL of CH₂ Cl₂, 3 mL of Et₃ N and 1.21 g of TsCl. Stir the mixture at room temperature for 1 h, then add 1 mL of MeOH and stir for 30 min. Add 1 g of LiCl and heat the mixture to 40° C. for 2.5 h. Filter and wash with CH₂ Cl₂ (2×15 mL). Combine the CH₂ Cl₂ washes, wash with NaHCO₃ and dry over Na₂ SO₄. Concentrate in vacuo to give the 21-chloride product.

EXAMPLE 1 ##STR17##

Dilute the 40 mL product solution from Preparation 1 with 100 mL of THF and cool to -85° to -83° C. Slowly add 20 g of PCl₅ (over a 30 min. period), while keeping the reaction temperature at -85° to -83° C. After 30 to 90 min., slowly pour the mixture into 800 mL of stirred water (at 10° to 15° C.). Stir the mixture at 10° to 15° C. for 30 min., then slowly add 32 mL of 50% NaOH (aqueous) to adjust to pH 7.5. Allow the mixture to stand at 10° to 15° C. for 30 min., then filter and wash the solids with 3×200 mL of water. Dry the solids in a vacuum oven at 60° C. overnight to give the triene product (92% overall yield from the starting trihydroxypregnadienedione of Preparation 1).

EXAMPLE 2 ##STR18##

Combine 10 g of the 11 -a-hydroxy steroid (isolated from the product solution of Preparation 1) and 65 mL of THF. Stir the mixture at room temperature to dissolve the steroid, then cool to -78° C. Add 8 g of PCl₅ in small portions over a period of 30 min. while maintaining the temperature below -73° C. Stir the mixture at -78°C. for 30 min., then add the mixture to 400 mL of water and stir for 30 min. at room temperature. Filter and wash the solids with 300 mL of water. Dry the solid under vacuum at 60° C. overnight to give 9.33 g of the title compound (94.5% molar yield). The ratio of Δ⁹,11 to Δ¹¹,12 steroid is 98:2.

Using the solvent and temperature indicated, and otherwise substantially the same procedure as described above, the following results were obtained:

    ______________________________________                                                Reaction   %      %      %                                              Solvent                                                                               Temp.      Δ.sup.9,11                                                                      Δ.sup.11,12                                                                     11β-Cl                                                                          Comment                                  ______________________________________                                         CH.sub.2 Cl.sub.2 /                                                                   room temp. 70.4   11.2   18.4                                           pyridine                                                                       pyridine                                                                              room temp. 52.3   3.8    43.9                                           CH.sub.2 Cl.sub.2                                                                     -20° C.                                                                            74.4   14.6   11.0                                           EtOAc  -20° C.                                                                            80.2   17.9   1.9                                            t-BuOMe                                                                               -45° C.                                                                            95.7   4.3    --    80% sm.sup.1                                                                   after 2 h                                DME    -45° C.                                                                            81.4   18.6   --                                             dioxane                                                                               room temp. 55.1   7.4    37.5                                           i-Pr.sub.2 O                                                                          -30° C.                                                                            94.0   6.0    --    85% sm.sup.1                                                                   after 0.5 h                              toluene                                                                               -45° C.                                                                            95.0   5.0    --    50% sm.sup.1                                                                   after 2 h                                CH.sub.3 CN                                                                           room temp. 82.8   1.8    3.1   (a)                                      THF    room temp. 81.1   7.6    11.3                                           THF    -20° C.                                                                            92.3   4.9    2.8                                            THF    -45° C.                                                                            95.5   3.3    1.2                                            THF    -78° C.                                                                            97.5   1.8    0.7                                            THF    -85° C.                                                                            98.4   1.3    0.3                                            ______________________________________                                          .sup.1 sm = unreacted starting material                                        (a) impurities were detected                                             

EXAMPLE 3 ##STR19##

Combine the 11-β-hydroxy steroid of Preparation 1A and 5 mL of THF. Cool to -78° C., add 0.1 g of PCl₅ and stir at -78° C. for 1 h. Add 0.1 g of PCl₅ and continue stirring at -78° C. for 1 h more. Warm the mixture to -60° and stir for another 1 h. Gradually warm the mixture to -50° C. while stirring for 3 h, then isolate the product as described in Example 2 to provide the title compound as a 93.5:6.5 mixture of Δ⁹,11 and Δ¹¹,12 steroids, respectively.

EXAMPLE 4 ##STR20##

Treat a solution of 11-α-hydroxy-16-α-methyl steroid of Preparation 1 B in 20 mL of THF, with 2 g of PCl₅ according to substantially the same procedure as described for Example 2 to provide the title compound (94% overall molar yield from starting trihydroxy steroid used in Preparation 1B). The ratio of Δ⁹,11 to Δ¹¹,12 steroid is 99:1.

EXAMPLE 5 ##STR21##

Combine 0.095 g of 11-β-chloro-17-α-hydroxy-16-β-methyl-21-ethoxycarbonyloxy-pregna-1,4-diene-3,20-dione and a mixture of 2 mL of DMSO. Heat the mixture at 90° C. for 160 h. to form the triene product. The reaction is monitored by HPLC (μ-Bondapak® C-18 column, 1:1 CH₃ CN/H₂ O, 1.7 mL/min). The starting compound (retention time 15.5-15.6 min.) is gradually converted to the triene product (retention time 10.47 min.) over the course of the reaction. The triene is formed in >97% yield as determined by HPLC (as described above). Essentially no Δ¹¹,12 steroid is formed.

Following substantially the same procedure, the results tabulated below were obtained using the solvents indicated:

    ______________________________________                                                     Reaction Reaction                                                  Solvent     Temp.    Time       Comments                                       ______________________________________                                         DMSO        110° C.                                                                          40 min     rxn. complete                                  EtOAc/pyridine                                                                             reflux   24 h       no reaction                                    CHCl.sub.3 /DBU                                                                            reflux   24 h       no reaction                                    THF/H.sub.2 O                                                                              reflux    3 h       no reaction                                    CH.sub.3 CN reflux    3 h       no reaction                                    CH.sub.3 CN/H.sub.2 O                                                                      reflux    8 h       rxn. complete                                  HOAc/H.sub.2 O                                                                             110° C.                                                                          40 min     rxn. complete                                  dioxane/H.sub.2 O                                                                          100° C.                                                                          3.5 h      rxn. complete                                  DMF         100° C.                                                                           5 h       rxn. complete                                  diglyme     100° C.                                                                           2 h       3% conversion                                  diglyme/H.sub.2 O                                                                          100° C.                                                                          <1 h       rxn. complete                                  ______________________________________                                    

EXAMPLE 6 ##STR22##

Combine 2 g of the 11-α-hydroxy steroid (isolated from the product solution of Preparation 1), 20 mL of CH₂ Cl₂ and 5 mL of pyridine and cool to -5° C. Slowly add (dropwise) 0.84 mL (2 equivalent) of POCl₃ and stir at room temperature for 24 h. Add 10 mL of pyridine and stir the mixture at 60° C. for 20 h, and analyze by HPLC. The ratio of Δ⁹,11 to Δ¹¹,12 is 98:2, and the solution yield is 13%.

EXAMPLE 7 ##STR23##

Combine 2 g of the 11-a-hydroxy steroid (isolated from the product solution of Preparation 1), 20 mL of THF and cool to -73° C. Add 0.5 mL (1.4 equivalents) of SO₂ Cl₂, stir for 20 min., then add 1.2 g of imidazole (4 equivalents). Stir the mixture for 1 h., then analyze by HPLC. The ratio of Δ⁹,11 to Δ¹¹,12 is 92.8:7.2.

EXAMPLE 8 ##STR24##

Combine 1 g of 16α-methyl-11α,17α, 21-trihydroxypregna-1,4-diene-3,20-dione, 0.73 g of PPh₃, 5 mL of CCl₄ and 5 mL of CH₃ CN, and stir the mixture at room temperature for 1 h. Add 0.25 g of PPh₃, stir 20 min. more. Analyze by HPLC to determine the extent of reaction. The product 21-chloride is 98% pure by HPLC.

EXAMPLE 9 ##STR25##

Combine 2.03 g of 16α-methyl-11α,17α, 21-trihydroxypregna-1,4-diene-3,20-dione, 4.01 g of PPh₃, 6 mL of CCl₄ and 12 mL of CH₃ CN, and stir the mixture at room temperature for 3 h. Heat the mixture at reflux overnight then analyze by HPLC to determine the extent of reaction. HPLC shows a 74% solution yield of the triene product.

EXAMPLE 10 ##STR26##

Combine 2 g of 16α-methyl-11α,17α, 21-trihydroxypregna-1,4-diene-3,20-dione, 1.05 g of imidazole, 15 mL of CH₂ Cl₂ and cool the mixture to -20° C. Add 0.45 mL of SO₂ Cl₂ and stir the mixture while monitoring by HPLC. Add water to quench the mixture, extract with CH₂ Cl₂. Wash the organic extract with NaHCO₃ (aqueous), then with water, and dry over Na₂ SO₄. Concentrate in vacuao to give the triene product (50% molar yield).

EXAMPLE 11 ##STR27##

Cool the product solution from Preparation 4° to -78° C., add 2 g of PCl₅ and stir the mixture at -78° C. to give a solution of the triene product. Analyze the product by HPLC. The ratio of Δ⁹,11 to Δ¹¹,12 is 98.6:1.4.

EXAMPLE 12 ##STR28##

Prepare a solution 2 g of the product of Preparation 5 in 20 mL of THF. Cool the solution to -78° C., add 2 g of PCl₅ and stir at -78° C. for 30 min. Add 20 mL of water, extract with CH₂ Cl₂ (2×30 mL) and wash the combined extracts with water. Dry over Na₂ SO₄ and concentrate in vacuo to give the triene product.

EXAMPLE 13 ##STR29##

Combine 2.03 g of 16α-methyl-11α,17α, 21-trihydroxy-pregna-1,4-diene-3,20-dione, 16 mL of CH₂ Cl₂, 50 mg of DMAP, 2 mL of Et₃ N and 1.23 g of TsCl. Stir the mixture at room temperature for about 1 h., then add 20 mL of water and adjust to pH=1 by adding HCl (aqueous). Extract with CH₂ Cl₂ (2×20 mL), combine the extracts and concentrate in vacuo to give a residue. Add 30 mL of THF to the residue and concentrate in vacuo. Add 20 mL of THF and 2.1 g of Li₂ CO₃, cool to -78° C. and add 2 g of PCl₅. Stir the mixture at -78° C. for 30 min., add 1 g of Li₂ CO₃, and warm to room temperature. Add 0.5 g of Li₂ CO₃ and stir the mixture overnight at room temp. Filter and add CH₂ Cl₂ and THF to bring the filtrate volume to 250 mL to give a solution of the product triene. The solution yield is 84.7% as determined by HPLC.

The reaction can also be run using about 3 g of Li₂ CO₃, which can be added in portions as described or can be added all at once prior to the addition of PCl₅.

EXAMPLE 14 ##STR30##

Combine 2 g of 16β-methyl-11α,17α, 21 -trihydroxy-pregna-1,4-diene-3,20-dione and 20 mL of THF and cool to -78° C. Add 2 g of PCl and stir for 20 min at -78° C. Pour the mixture into water, filter and wash the solids with water to give the phosphate dimer product. FAB MS: 775 (M⁺ +1); FAB MS (NaCl): 797 (M+Na⁺). 

We claim:
 1. A process for regioselectively preparing a 21-chloro steroid of the formula ##STR31## wherein one of R² or R³ is CH₃ and the other is H, comprising treating a triol of the formula ##STR32## wherein R² and R³ are as defined above, with triphenylphosphine and CCl₄ at a temperature of -20° to +40° C.
 2. A process for regioselectively preparing a 21 -chloro steroid of the formula ##STR33## wherein one of R² or R³ is CH₃ and the other is H, comprising treating a triol of the formula ##STR34## wherein R² and R³ are as defined above, with p-toluenesulfonyl chloride and a tertiary amine base and then with LiCl. 